Polyolefin-acrylic particles

ABSTRACT

Provided is a dispersion of composite particles in an aqueous medium, wherein the composite particles comprise
         (I) a crosslinked polyolefin core, and   (II) a full or partial shell comprising polymerized units of one of more vinyl monomers.

Particles that contain polyolefin are useful for a variety of purposes.For example, composite particles may be formed in which a full orpartial shell of (meth)acrylic polymer resides on a polyolefin core.Such composite particles may be used as additives to matrix polymerssuch as polycarbonate, to improve the impact resistance or otherproperties.

US 2016/0177077 describes composite polymer compositions comprising theemulsion polymerization product of an aqueous polyolefin dispersion andone or more (meth)acrylic monomers. It is desired to provide improvedpolyolefin particles and to provide a process for making improvedpolyolefin particles, so that when a shell of (meth)acrylate polymer isformed on the improved polyolefin particles, and the resulting compositeparticles are added to a matrix polymer such as, for example,polycarbonate, to form compounded matrix polymer, one or more of thefollowing benefits is obtained: the impact resistance of thepolycarbonate is improved; the compounded matrix polymer has melt flowcharacteristics similar to the original matrix polymer, as measured bythe melt flow rate; the compounded matrix polymer, including the addedpolyolefin particles, resists weathering well; and/or molded parts madefrom matrix polymer compounds have few or no surface defects (such as,for example, delamination).

The following is a statement of the invention.

A first aspect of the present invention is a method of making apolymeric composition comprising

-   -   (a) providing a dispersion of initial polyolefin particles in an        aqueous medium, wherein the initial polyolefin particles        comprise        -   (i) one or more hydrocarbon polyolefin,        -   (ii) one or more non-hydrocarbon polyolefin, and        -   (iii) one or more crosslinking agent;    -   (b) contacting the initial polyolefin particles with a peroxide        initiator to form crosslinked polyolefin particles.

A second aspect of the present invention is a process for making adispersion of composite particles comprising

-   -   (i) providing a dispersion of crosslinked polyolefin particles        in an aqueous medium,    -   (ii) performing emulsion polymerization on one or more vinyl        monomers in the presence of the crosslinked polyolefin particles        to produce the dispersion of composite particles.

A third aspect of the present invention is a dispersion of compositeparticles in an aqueous medium, wherein the composite particles comprise

-   -   (I) a crosslinked polyolefin core, and    -   (II) a full or partial shell comprising polymerized units of one        of more vinyl monomers.

A fourth aspect of the present invention is a method of modifyingpolycarbonate comprising blending the polycarbonate with compositeparticles, wherein the composite particles comprise

-   -   (I) a crosslinked polyolefin core, and    -   (II) a full or partial shell comprising polymerized units of one        of more vinyl monomers.

The following is a detailed description of the invention.

As used herein, the following terms have the designated definitions,unless the context clearly indicates otherwise.

A hydrocarbon is a compound containing only atoms of hydrogen andcarbon. An atom other than carbon and hydrogen is a “hetero” atom. Achemical group that contains one or more hetero atom is a “hetero”group.

A “polymer,” as used herein is a relatively large molecule made up ofthe reaction products of smaller chemical repeat units. Polymers mayhave structures that are linear, branched, star shaped, looped,hyperbranched, crosslinked, or a combination thereof; polymers may havea single type of repeat unit (“homopolymers”) or they may have more thanone type of repeat unit (“copolymers”). Copolymers may have the varioustypes of repeat units arranged randomly, in sequence, in blocks, inother arrangements, or in any mixture or combination thereof. Polymershave weight-average molecular weight of 1,000 daltons or higher.Polymers that are sufficiently crosslinked that they become insoluble inany solvent are considered to have infinite molecular weight.

Molecules that can react with each other to form the repeat units of apolymer are known herein as “monomers.” The repeat units so formed areknown herein as “polymerized units” of the monomer.

Vinyl monomers have the structure

where each of R¹, R², R³, and R⁴ is, independently, a hydrogen, ahalogen, an aliphatic group (such as, for example, an alkyl group), asubstituted aliphatic group, an aryl group, a substituted aryl group,another substituted or unsubstituted organic group, or any combinationthereof. Vinyl monomers are capable of free radical polymerization toform polymers. Some vinyl monomers have one or more polymerizablecarbon-carbon double bonds incorporated into one or more of R¹, R², R³,and R⁴; such vinyl monomers are known herein as multifunctional vinylmonomers. Vinyl monomers with exactly one polymerizable carbon-carbondouble bond are known herein as monofunctional vinyl monomers.

An olefin monomer is a monomer that is a hydrocarbon having one or morecarbon-carbon double bond and having no aromatic rings.

Vinyl monomers that are hydrocarbons are olefin monomers. A polymerhaving more than 50% by weight polymerized units of olefin monomers is apolyolefin. Vinyl aromatic monomers are vinyl monomers in which one ormore of R¹, R², R³, and R⁴ contains one or more aromatic rings.(Meth)acrylate means acrylate or methacrylate. (Meth)acrylic meansacrylic or methacrylate. (Meth)acrylic monomers are monomers selectedfrom acrylic acid, methacrylic acid, alkyl esters thereof,substituted-alkyl esters thereof, amides thereof, N-substituted amidesthereof, acrylonitrile, methacrylonitrile, and mixtures thereof.Substituents may be, for example, hydroxyl groups, alkyl groups,aromatic groups, groups containing non-aromatic carbon-carbon doublebonds, or other groups, or combinations thereof. A (meth)acrylic polymeris a polymer having more than 50% by weight polymerized units of(meth)acrylic monomers.

An alpha-olefin is a hydrocarbon having 3 or more carbon atoms andhaving exactly one carbon-carbon double bond, which is located at aterminal carbon atom. That is, in an alpha-olefin, at least one of thetwo carbon atoms in the carbon-carbon double bond also has two hydrogenatoms attached. A diene is a hydrocarbon having exactly twocarbon-carbon double bonds. A diene may be conjugated or non-conjugated.

A polyolefin that is made exclusively of hydrocarbon monomers isconsidered to be a hydrocarbon, even if a small number of hetero groupsis attached to the polyolefin, as fragments from an initiator and/orchain transfer agent. In hydrocarbon polyolefins, the mole ratio ofhetero atoms to polymerized units of all monomers is 0.001:1 or lower. Apolyolefin that is not a hydrocarbon is a non-hydrocarbon polyolefin.

As used herein, a crosslinking agent is a compound having two or morecarbon-carbon double bonds.

A dispersion is a collection of particles that are distributedthroughout a continuous liquid medium. A continuous liquid medium is anaqueous medium if the liquid medium is 50% or more water by weight basedon the weight of the liquid medium. A dispersion has “solids” contentthat is determined by weighing the dispersion (WDISP), then drying thedispersion in an infrared moisture balance at 150° C. until the weightis stable, then determining the weight of the dry residue (WDRY), andthen solids=100*WDRY/WDISP.

A compound is said herein to be water soluble if the amount of thecompound that may be dissolved in 100 g of water at 23° C. is 5 grams ormore.

An initiator is a compound that, when exposed to initiation conditions,produces radical moieties that are capable of initiating free-radicalpolymerization. The nature of the initiation condition varies amonginitiators. Some examples: thermal initiators produce radical moietieswhen heated to a sufficiently high temperature; and photoinitiatorsproduce radical moieties when exposed to radiation of sufficiently shortwavelength and sufficiently high intensity. As another example, a redoxinitiator is a pair of molecules that react together in anoxidation/reduction reaction to produce radical moieties; initiationconditions obtain when both members of the pair are present and canreact with each other.

Emulsion polymerization is a process in which monomer emulsion droplets,water-soluble initiator, and optional seed particles are present in anaqueous medium. During emulsion polymerization, monomer moleculestransfer from the monomer emulsion droplets to the particles wherepolymerization takes place, which may be separate particles formedduring polymerization or may be the seed particles, or a combinationthereof.

Polymers may be characterized by their glass transition temperature(Tg), which is measured by differential scanning calorimetry (DSC), at ascan rate of 10° C./min, using the inflection point method.

A collection of particles may be characterized by the volume meandiameter.

Ratios are characterized herein as follows. For example, if a ratio issaid to be 5:1 or higher, it is meant that the ratio may be 5:1 or 6:1or 100:1 but may not be 4:1. To state this characterization in a generalway, if a ratio is said to be X:1 or higher, then the ratio is Y:1,where Y is greater than or equal to X. Similarly, for example, if aratio is said to be 2:1 or lower, it is meant that the ratio may be 2:1or 1:1 or 0.001:1 but may not be 3:1. To state this characterization ina general way, if a ratio is said to be Z:1 or lower, then the ratio isW:1, where W is less than or equal to Z.

The present invention involves the use of a dispersion of “initial”polyolefin particles. The label “initial” distinguishes the polyolefinparticles from various polyolefin particles that are formed as a resultof operations performed on the initial polyolefin particles. Preferably,the solids of the dispersion of initial polyolefin particles is 70% orless; more preferably 60% or less. Preferably, the solids of thedispersion of initial polyolefin particles is 40% or more; morepreferably 50% or more.

Preferably, the amount of water in the aqueous medium, by weight basedon the weight of the aqueous medium, is 60% or more; more preferably 70%or more; more preferably 80% or more; more preferably 90% or more.

Preferably, the volume average particle diameter of the dispersion ofinitial polyolefin particles is 100 nm or larger; more preferably 150 nmor larger; more preferably 200 nm or larger; more preferably 250 nm orlarger. Preferably, the volume average particle diameter of thedispersion of initial polyolefin particles is 2000 nm or smaller; morepreferably 1000 nm or smaller; more preferably 750 nm or smaller; morepreferably 500 nm or smaller.

The amount of total polyolefin in the initial polyolefin particles is,by weight based on the total solid weight of the dispersion, preferably50% or more; more preferably 60% or more; more preferably 70% or more;more preferably 80% or more. The amount of total polyolefin polymer inthe initial polyolefin particles is, by weight based on the total solidweight of the dispersion, preferably 98% or less; more preferably 96% orless. Initial polyolefin particles preferably contain one or morehydrocarbon polyolefin and one or more non-hydrocarbon polyolefin.

The initial polyolefin particles preferably have Tg of 50° C. or lower;more preferably 30° C. or lower; more preferably 15° C. or lower; morepreferably 0° C. or lower; more preferably −15° C. or lower.

Examples of hydrocarbon polyolefins include, but are not limited to,homopolymers and copolymers (including elastomers) of monomers chosenfrom ethylene and one or more alpha-olefins. Examples of alpha-olefinsinclude propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene,3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, and1-dodecene. Further examples of hydrocarbon polyolefins includecopolymers (including elastomers) of one or more dienes with ethylene,with one or more alpha-olefins, or with a combination thereof. Examplesof dienes include butadiene; dicyclopentadiene; 1,5-hexadiene;ethylidene norbornene; and vinyl norbornene.

Preferred hydrocarbon polyolefins are copolymers of two or morealpha-olefins and copolymers of ethylene with one or more alpha-olefins.More preferred are copolymers of ethylene with one or morealpha-olefins. Among copolymers of ethylene with one or morealpha-olefins, preferably an alpha-olefin is used that has 5 or morecarbon atoms, more preferably 6 or more carbon atoms; more preferably 7or more carbon atoms; more preferably 8 or more carbon atoms. Amongcopolymers of ethylene with one or more alpha-olefins, preferably analpha-olefin is used that has 12 or fewer carbon atoms; more preferably10 or fewer carbon atoms; more preferably 9 or fewer carbon atoms; morepreferably 8 or fewer carbon atoms.

Polyolefins that are copolymers may be statistical copolymers, blockcopolymers, graft copolymers, copolymers having other structure, ormixtures thereof. Preferred are statistical copolymers.

Some suitable hydrocarbon polyolefins are commercially available fromThe Dow Chemical Company, under the tradename VERSIFY™, NORDEL™, orENGAGE™; or from ExxonMobil Chemical Company, under the tradenameVISTAMAXX™, VISTALON™, or EXACT™.

Some suitable hydrocarbon polyolefins are copolymers of one or moreolefin monomers with one or more vinyl aromatic monomers. Among suchcopolymers are, for example, copolymers of ethylene and styrene andblock copolymers of styrene-olefin monomer(s)-styrene, including, forexample, styrene-butadiene-styrene, styrene-isoprene-styrene,styrene-isoprene-butadiene-styrene, and the hydrogenated versions ofthese block copolymers, including styrene-ethylene-butylene-styrene,styrene-ethylene-propylene-styrene, andstyrene-ethylene-ethylene-propylene-styrene.

The amount of hydrocarbon polyolefin in the initial polyolefin particlesis, by weight based on the total solid weight of the dispersion ofinitial polyolefin particles, preferably 50% or more; more preferably60% or more; more preferably 65% or more. The amount of hydrocarbonpolyolefin in the initial polyolefin particles is, by weight based onthe total solid weight of the dispersion of initial polyolefinparticles, preferably 95% or less; more preferably 90% or less; morepreferably 85% or less.

The initial polyolefin particles preferably contain one or morenon-hydrocarbon polyolefin. Non-hydrocarbon polyolefins contain one ormore hetero group (as defined above). The hetero group may have beenattached to a comonomer prior to polymerization or may have been addedto the polyolefin by grafting after polymerization.

Examples of non-hydrocarbon polyolefins are copolymers of one or morealpha-olefin with one or more non-hydrocarbon vinyl monomer. Examples ofnon-hydrocarbon vinyl monomers are vinyl acetate, ethyl acrylate, vinylalcohol, vinyl chloride, and (meth)acrylic monomers.

Among non-hydrocarbon polyolefins, preferred hetero groups are carboxylgroups, ester groups, anhydride groups, alkoxysilane groups, andcombinations thereof. More preferred are anhydride groups; morepreferred is the product of grafting maleic anhydride onto a hydrocarbonpolyolefin. Preferred hydrocarbon polyolefins onto which hetero groupsmay be grafted are preferably polyethylene or alpha-olefin homopolymers,more preferably polyethylene. An unsaturated compound containing ahetero atom may be grafted to a hydrocarbon polyolefin by any effectivemethod, for example by a free radical method, for example in thepresence of a free radical initiator or in the presence of ionizingradiation.

Some suitable non-hydrocarbon polyolefins include, for example, theAMPLIFY™ polymers, PARALOID™ functionalized ethylene-octene copolymers,and RETAIN™ polymers (available from The Dow Chemical Company).Additional examples include FUSABOND™ polymers (available from E.I.DuPont de Nemours), EXXELOR™ polymers (available from ExxonMobilChemical Company), POLYBOND™ polymers (available from ChemturaCorporation), and LICOCENE™ polymers (available from ClariantInternational Ltd.).

The amount of non-hydrocarbon polyolefin in the initial polyolefinparticles is, by weight based on the total solid weight of thedispersion of initial polyolefin particles, preferably 2% or more; morepreferably 4% or more; more preferably 8% or more. The amount ofnon-hydrocarbon polyolefin in the initial polyolefin particles is, byweight based on the total solid weight of the dispersion of initialpolyolefin particles, preferably 49.5% or less; more preferably 40% orless; more preferably 30% or less; more preferably 25% or less; morepreferably 20% or less.

The dispersion of initial polyolefin particles additionally contains acrosslinking agent. Preferred crosslinking agents are chosen frompolyolefins having carbon-carbon double bonds (“polyolefin crosslinkingagents”) and compounds having molecular weight of 500 or less and havingtwo or more carbon-carbon double bonds (“monomer crosslinking agents”).Among polyolefin crosslinking agents, preferred are homopolymers andcopolymers that contain polymerized units of one or more diene. Amongmonomer crosslinking agents, preferred are those with two or morecarbon-carbon double bonds; more preferably 3 or more carbon-carbondouble bonds. Suitable monomer crosslinking agents include triallylisocyanurate and1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane.

The amount of crosslinking agent is, by weight based on the total solidweight of the dispersion of initial polyolefin particles, preferably0.5% or more; more preferably 1% or more; more preferably 1.5% or more.The amount of crosslinking agent is, by weight based on the total solidweight of the dispersion of initial polyolefin particles, preferably 20%or less; more preferably 15% or less.

The dispersion of initial polyolefin particles preferably contains oneor more surfactant. Preferred surfactants are anionic surfactants, whichhave a hydrocarbon group of 8 or more carbon atoms and an anionic group.The hydrocarbon group may be linear, branched, aromatic, or acombination thereof; preferred are linear hydrocarbon groups. An anionicgroup is a chemical group that, in water at pH of 7, carries a negativecharge. Preferred anionic groups are phosphate groups, phosphonategroups, carboxylate groups, sulfate groups, and sulfonate groups; morepreferred are sulfate groups. Preferred anionic surfactants also containthe group —(CH₂CH₂O)_(n)—. When the group —(CH₂CH₂O)_(n)— is present, itis preferably bonded to the sulfate group. The index n is 1 or more,preferably 2 or more. The index n is preferably 20 or less; morepreferably 15 or less; more preferably 10 or less; more preferably 6 orless; more preferably 4 or less; more preferably 3 or less.

The amount of surfactant in the initial polyolefin particles is, byweight based on the total solid weight of the dispersion, preferably0.5% or more; more preferably 1% or more; more preferably 2% or more;more preferably 3% or more. The amount of surfactant in the initialpolyolefin particles is, by weight based on the total solid weight ofthe dispersion, preferably 10% or less; more preferably 8% or less; morepreferably 6% or less; more preferably 4% or less.

The initial polyolefin particles optionally contain one or more oil, oneor more silicon-containing polymer (such as, for example,polydimethylsiloxane), or a mixture thereof.

Preferably, the total amount of the sum of hydrocarbon polyolefins,nonhydrocarbon polyolefins, crosslinking agents, and surfactants, byweight based on the total solids weight of the dispersion of initialpolyolefin particles, is 40% or more; more preferably 50% or more; morepreferably 60% or more; more preferably 70% or more; more preferably 80%or more; more preferably 90% or more; more preferably 95% or more.

The dispersion of initial particles in an aqueous medium may be formedby any method. One example of a suitable method is as follows. Ahydrocarbon polyolefin and a non-hydrocarbon polyolefin are fed via afeed throat into an extruder. The hydrocarbon polyolefin and thenon-hydrocarbon polyolefin may be added separately to the extruder; maybe mixed together and then added to the extruder as a mixture; or may becompounded together by melt mixing prior to addition to the extruder. Ifa crosslinking agent is used that is solid at 25° C., then thatcrosslinking agent is also fed via the feed throat along withhydrocarbon polyolefin and non-hydrocarbon polyolefin. If a crosslinkingagent is used that is liquid at 25° C., then that crosslinking agent isinjected via a pump into the melt zone of the extruder. The polyolefins,including the crosslinking agent, are mixed together in the melt statein the extruder and then emulsified in the extruder by the addition ofwater and surfactant via pumps. The emulsion thus formed has solidslevel of 70% or higher. One method of making such an emulsion is taughtin US 2016/0177077. Then further water is added to the extruder, and thefinal dispersion exiting the extruder has solids level of less than 70%.

Also contemplated is a method in which polyolefins are first emulsifiedas above, and then the crosslinking agent is added to the emulsion,preferably when the emulsion is held at a temperature above the meltingpoint of one or more of the polyolefins.

A preferred method of making crosslinked particles contains a step ofcontacting the dispersion of initial polyolefin particles with aperoxide initiator. Peroxide initiators have the structure R¹—O—O—R²,where R¹ and R² are each independently H or an organic group. PreferablyR¹ and R² are each independently H or an alkyl group. Preferably R¹ andR² are not both H. Preferably R¹ is H. Preferably R² is an alkyl groupwith 2 or more carbon atoms; more preferably 3 or more carbon atoms,more preferably 4 or more carbon atoms. Preferably R² is an alkyl groupwith 12 or fewer carbon atoms; more preferably 10 or fewer carbon atoms;more preferably 8 or fewer carbon atoms; more preferably 6 or fewercarbon atoms; more preferably 4 or fewer carbon atoms.

Preferred peroxide initiators are water soluble. Preferred peroxideinitiators are hydrogen peroxide and alkyl hydroperoxides; morepreferred is t-butyl hydroperoxide.

Preferably, a reducing agent is also included to form a redox initiatorwith the peroxide. Preferred reducing agents are water soluble.Preferred reducing agents are ascorbic acid, isoascorbic acid, sodiumformaldehyde sulfoxylate, tetramethyl ethylene diamine, sodiummetabisulfites, and mixtures thereof; more preferred is isoascorbicacid. Preferably a catalyst for the oxidation/reduction reaction betweenthe peroxide and the reducing agent is also included. Preferred catalystis a salt of iron (II); more preferred is FeSO₄. Preferably the moleratio of peroxide to reducing agent is 0.7:1 or higher; more preferably0.8:1 or higher; more preferably 0.9:1 or higher. Preferably the moleratio of peroxide to reducing agent is 1.3:1 or lower; more preferably1.2:1 or lower; more preferably 1.1:1 or lower.

The amount of peroxide is preferably, by weight based on the total solidweight of the dispersion of initial polyolefin particles, 0.02% or more;more preferably 0.05% or more; more preferably 0.1% or more. The amountof peroxide is preferably, by weight based on the total solid weight ofthe dispersion of initial polyolefin particles, 2% or less; morepreferably 1% or less; more preferably 0.5% or less. The mole ratio ofreducing agent to peroxide is preferably 0.2:1 or higher; morepreferably 0.5:1 or higher; more preferably 0.8:1 or higher. The moleratio of reducing agent to peroxide is preferably 2:1 or lower; morepreferably 1.5:1 or lower; more preferably 1.2:1 or lower. The amount ofcatalyst is, by weight based on the solid weight of the dispersion ofinitial polyolefin particles, preferably 1 ppm or more; more preferably2 ppm or more; more preferably 4 ppm or more. The amount of catalyst is,by weight based on the solid weight of the dispersion of initialpolyolefin particles, preferably 50 ppm or less; more preferably 20 ppmor less; more preferably 10 ppm or less.

While the invention is not limited to any specific mechanism, it iscontemplated that the initiator generates free radical moieties thatinteract with the double bonds in the crosslinking agent and cause themto attach to polymer chains in the hydrocarbon polyolefin, thus creatingcrosslinks between polymer chains in the hydrocarbon polyolefin. Thisinteraction is known herein as the crosslinking reaction. If a thermalinitiator is used, it is expected that the dispersion will be heated toa temperature sufficiently high that the initiator will generateradicals for the crosslinking reaction. If a photoinitiator is used, itis expected that the dispersion will be exposed to radiation ofsufficiently short wavelength and of sufficient intensity that theinitiator will generate radicals for the crosslinking radicals. If aredox initiator is used, it is expected that the oxidation/reductionreaction will generate radicals for the crosslinking radicals. Redoxinitiators are preferred.

After the crosslinking reaction is complete, the particles in thedispersion are now referred to as crosslinked polyolefin particles.Preferably, the crosslinked polyolefin particles remain as a dispersionin the aqueous medium.

The crosslinked polyolefin particles preferably have Tg of 50° C. orlower; more preferably 30° C. or lower; more preferably 15° C. or lower;more preferably 0° C. or lower; more preferably −15° C. or lower.

Preferably, the volume average particle diameter of the crosslinkedpolyolefin particles is 100 nm or larger; more preferably 150 nm orlarger; more preferably 200 nm or larger; more preferably 250 nm orlarger. Preferably, the volume average particle diameter of thecrosslinked polyolefin particles is 2000 nm or smaller; more preferably1000 nm or smaller; more preferably 750 nm or smaller; more preferably500 nm or smaller.

In the dispersion of crosslinked polyolefin particles, preferably theamount of water, by weight based on the weight of the aqueous medium, is60% or more; more preferably 70% or more; more preferably 80% or more;more preferably 90% or more.

Preferably, the solids of the dispersion of crosslinked polyolefinparticles is 20% or more; more preferably 25% or more; more preferably30% or more; more preferably 35% or more. Preferably, the solids of thedispersion of crosslinked polyolefin particles is 60% or less; morepreferably 55% or less; more preferably 50% or less; more preferably 45%or less.

The extent of crosslinking is assessed by measuring the gel fraction ofthe particles. The gel fraction is measured by drying the dispersion toremove the water, weighing the dry residue (weight=WTOT), then mixingthe dry residue with toluene at 90° C. for 1 hour, then filtering thehot toluene through porous metal column fits of 75 μm pore size, asexplained in detail in “method B” in the Examples below. The residualsolid material not dissolved in the toluene is considered “gel” orcrosslinked polymer. The gel fraction is the weight of dry gel (afterremoval of residual toluene) (weight=WGEL) divided by the weight of thetotal solid portion of the dispersion, expressed as a percentage. Thatis,

gel fraction=100*WGEL/WTOT.

Preferably, the gel fraction is 5% or higher; more preferably 10% orhigher; more preferably 15% or higher.

The dispersion of crosslinked polyolefin particles may be used for anypurpose. A preferred purpose is as an ingredient in a process for makinga dispersion of composite particles in an aqueous medium. A preferredprocess for making a dispersion of composite particles in an aqueousmedium is to perform emulsion polymerization on one or more vinylmonomers in the presence of the dispersion of crosslinked polyolefinparticles.

Preferably, one or more vinyl monomers are mixed with water and one ormore surfactant to form an emulsion of droplets in an aqueous medium,where the droplets contain (meth)acrylic monomer. Preferably, a mixtureis formed that contains a dispersion of crosslinked polyolefin particlesin an aqueous medium, the emulsion of vinyl monomer droplets, and one ormore water soluble initiator. The mixture is subjected to conditionsthat cause the initiator to produce radicals. Those conditions may beestablished at the same time the ingredients are mixed together, orthose conditions may be established after some or all of the ingredientshave been mixed together.

For example, the emulsion polymerization could be performed as a “batch”process. In a batch process, all of the desired dispersion ofcrosslinked polyolefin particles and all of the desired vinyl monomer(s)are mixed together. Then conditions are established to cause initiatorto create radicals, for example by having a water-soluble thermalinitiator present in the mixture and then heating the mixture, or byadding a redox initiator combination to the mixture. The radicals theninitiate polymerization of the vinyl monomer in the presence of thecrosslinked polyolefin particles.

A preferred emulsion polymerization method is “gradual addition.” In agradual addition process, all of the desired dispersion of crosslinkedpolyolefin particles are placed in a vessel. Then, one or more emulsionof vinyl monomer(s) are gradually added to the vessel, under conditionsin which an initiator is producing radicals. In a preferred version ofgradual addition, at the same time the one or more emulsion of vinylmonomers is being added, one or more water soluble initiators are alsobeing added. If the water soluble initiator is a thermal initiator, themixture in the vessel is preferably at a temperature sufficiently highto make the initiator produce radicals. If the water-soluble initiatoris a redox initiator, preferably the various compounds of the redoxinitiator are simultaneously fed to the reactor gradually, preferablyseparately. In a gradual addition process, preferably the time from theaddition of the first amount of monomer until the cessation of theaddition of monomer is preferably 10 minutes or more; more preferably 20minutes or more; more preferably 30 minutes or more; more preferably 40minutes or more; more preferably 50 minutes or more.

Preferred vinyl monomers are (meth)acrylic monomers, vinyl aromaticmonomers, and mixtures thereof; more preferred are (meth)acrylicmonomers. Among (meth)acrylic monomers, preferred are (meth)acrylicacid, unsubstituted alkyl esters thereof, substituted-alkyl estersthereof, and mixtures thereof; more preferred are (meth)acrylic acid,unsubstituted alkyl esters thereof, and mixtures thereof; more preferredare unsubstituted alkyl esters of (meth)acrylic acid. Amongunsubstituted alkyl esters of acrylic acid, preferred are those in whichthe alkyl group has 2 or more carbon atoms, more preferably 3 or morecarbon atoms, more preferably 4 or more carbon atoms. Amongunsubstituted alkyl esters of acrylic acid, preferred are those in whichthe alkyl group has 18 or fewer carbon atoms; more preferably 12 orfewer carbon atoms; more preferably 8 or fewer carbon atoms. Amongunsubstituted alkyl esters of methacrylic acid, preferred are those inwhich the alkyl group has 4 or fewer carbon atoms; more preferably 3 orfewer carbon atoms; more preferably 2 or fewer carbon atoms; morepreferably 1 carbon atom.

Optionally the vinyl monomers used in the emulsion polymerizationcontain one or more monofunctional monomer and one or moremultifunctional monomer.

Preferably, the emulsion polymerization of vinyl monomer(s) forms avinyl polymer that has a glass transition that is distinct from theglass transition of the crosslinked polyolefin particles. Preferably,the Tg of the vinyl polymer is higher than 50° C.; more preferablyhigher than 75° C.

Preferably, the vinyl polymer forms on the surfaces of the particles ofcrosslinked polyolefin. It is contemplated that the vinyl polymer formsa full or partial shell around particles of crosslinked polyolefin. Thecrosslinked polyolefin particle with a full or partial shell of vinylpolymer is called herein a composite particle. Preferably, at theconclusion of the emulsion polymerization process, the compositeparticles are dispersed in an aqueous medium. The crosslinked polyolefinparticle is then referred to herein as the “core.” The vinyl polymerformed during the emulsion polymerization is referred to herein as the“shell.”

Preferably, the volume average particle diameter of the compositeparticles is 100 nm or larger; more preferably 150 nm or larger; morepreferably 200 nm or larger; more preferably 250 nm or larger.Preferably, the volume average particle diameter of the compositeparticles is 2000 nm or smaller; more preferably 1000 nm or smaller;more preferably 750 nm or smaller; more preferably 500 nm or smaller.

In the dispersion of composite particles, preferably the amount ofwater, by weight based on the weight of the aqueous medium, is 60% ormore; more preferably 70% or more; more preferably 80% or more; morepreferably 90% or more.

Preferably, the solids of the dispersion of composite particles is 20%or more; more preferably 25% or more; more preferably 30% or more; morepreferably 35% or more. Preferably, the solids of the dispersion ofcomposite particles is 60% or less; more preferably 55% or less; morepreferably 50% or less; more preferably 45% or less.

Preferably, the composite particles show two separate Tg's. It isexpected that one Tg is a characteristic of the polyolefin core whilethe other Tg is a characteristic of the vinyl polymer shell. Preferably,the Tg of the polyolefin core is 50° C. or lower; more preferably 30° C.or lower; more preferably 15° C. or lower; more preferably 0° C. orlower; more preferably −15° C. or lower. Preferably, the Tg of the vinylpolymer shell is higher than 50° C.; more preferably 60° C. or higher;more preferably 70° C. or higher.

Preferably some of the vinyl polymer of the shell is grafted to thepolyolefin core. That is, preferably, some of the polymer chains of thevinyl polymer shell are covalently attached to one or more of thepolymer chains in the polyolefin core. The extent of grafting may beassessed using the method described below in the Examples. Preferablythe amount of shell that is grafted to the core, by weight based on thetotal amount of the shell, is 40% or more; more preferably 50% or more;more preferably 60% or more; more preferably 70% or more; morepreferably 80% or more; more preferably 90% or more.

The relative amounts of polyolefin core and vinyl polymer shell may becharacterized by the weight of core, expressed as a percentage based onthe sum of the weights of the core and the shell. The weight of theshell is deduced from the weight of all (meth)acrylic polymers added tothe reaction vessel during emulsion polymerization. Preferably theamount of core is 95% or less; more preferably 92% or less; morepreferably 87% or less. Preferably the amount of core is 60% or more;more preferably 70% or more; more preferably 77% or more.

Optionally, one or more buffer may be added to the dispersion ofcomposite particles in order to adjust the pH of the dispersion.

A dispersion of composite particles according to the present inventionmay be used for any purpose. For some purposes, it is desirable toremove water from the dispersion and create a powder that contains thecomposite particles. Suitable methods for removing water from thedispersion of composite particles include, for example, spray drying andcoagulation. When coagulation is used, it is preferably followed bysubsequent drying methods including, for example, filtration, fluid beddrying, and combinations thereof. Preferably the process of removingwater results in a powder in which the powder particles containcomposite particles. It is expected that each particle in the powderwill contain many composite particles. A powder particle will oftencontain 1000 or more composite particles.

The collection of powder particles optionally contains additionalingredients. Additional ingredients may be added to the dispersion anddried along with the composite particles, or additional ingredients maybe added to the powder particles after the drying process. For example,one or more antioxidants or one or more process stabilizers or acombination thereof may be added to the collection of powder particles.Preferred process stabilizers contained in the collection of powderparticles are phosphate salts; more preferred is sodium phosphate.

A powder that contains the composite particles of the present inventionmay be used for any purpose. One preferred use of such a powder is as anadditive to a matrix polymer. Preferably, the powder that contains thecomposite particles of the present invention is mixed with powder orpellets of the matrix polymer, and the two ingredients, along withoptional additional ingredients, are heated and mechanically blended,for example in an extruder. Preferably, the individual compositeparticles of the present invention become dispersed throughout acontinuous phase of the matrix polymer.

The matrix polymer may be any type of polymer. Preferred matrix polymersare polycarbonates, polyvinyl chloride, nylon, polyurethane, naturalrubber, synthetic rubber, polystyrene, (meth)acrylate polymers,polyesters, phenol-formaldehyde polymers, epoxies, polystyrene,copolymers of polystyrene, copolymers thereof, and blends thereof.Copolymers of polystyrene include, for example, styrene/acrylonitrile(SAN) and acrylonitrile/butadiene/styrene (ABS). Preferred arepolycarbonates, polyvinyl chloride, polyesters, copolymers ofpolystyrene, and blends thereof. Blends include, for example, blends ofpolycarbonate with ABS and blends of polycarbonate with polyesters. Morepreferred are matrix polymers that comprise polycarbonate; morepreferably matrix polymers that comprise polycarbonate in an amount, byweight based on the weight of the matrix polymer, of 20% or more; morepreferably 40% or more; more preferably 60% or more; more preferably 80%or more; more preferably 90% or more; more preferably 95% or more. Somesuitable matrix polymers are blends of polycarbonate with a copolymer ofstyrene, acrylonitrile, and butadiene; and blends of polycarbonate witha polyester such as, for example, butylene terephthalate.

In a composition that contains composite particles of the presentinvention and matrix polymer, the amount of composite particles ischaracterized as a weight percentage, based on the sum of the weights ofthe composite particles and the matrix polymer. Preferably, the amountof composite particles is 0.5% or more; more preferably 1% or more; morepreferably 1.5% or more; more preferably 2% or more. Preferably, theamount of composite particles is 40% or less; more preferably 30% orless; more preferably 20% or less; more preferably 15% or less; morepreferably 10% or less; more preferably 7% or less.

A composition containing matrix polymer and composite particles of thepresent invention is known herein as compounded matrix polymer.Optionally, additional ingredients in addition to the matrix polymer andthe composite particles may be present in the compounded matrix polymer.Such additional ingredients may be added at any point in the process ofmaking the compounded matrix polymer. For example, the processstabilizers described above as present in the powder form of thecomposite particles are optionally present in the compounded matrixpolymer. Other process additional ingredients may be added duringcompounding (that is, when the composite particles are mixed with thematrix polymer). Additional ingredients suitable for addition duringcompounding include, for example process stabilizers (such as, forexample, organic phosphates) and antioxidants.

When process stabilizers are present, preferably the amount of processstabilizer, by weight based on the weight of the compounded matrixpolymer, is 0.05% or more; more preferably 0.1% or more. When processstabilizers are present, preferably the amount of process stabilizer, byweight based on the weight of the compounded matrix polymer, is 0.5% orless; more preferably 0.3% or less.

The following are examples of the present invention.

Test methods include the following: melt flow rate (MFR) was measuredaccording to ISO 1133; Notched Izod Impact Strength was measuredaccording to ASTM D256; yellowness index was measured according to ASTME313.

The following materials were used:

Hydrocarbon Polyolefins:

-   -   E/OCT-1=ENGAGE™ 8407 ethylene/octene copolymer from the Dow        Chemical Company    -   E/OCT-2=ENGAGE™ 8137 ethylene/octene copolymer from the Dow        Chemical Company    -   E/OCT-3=ENGAGE™ 8842 ethylene/octene copolymer from the Dow        Chemical Company

Non-Hydrocarbon Polyolefins

-   -   PE/MAH-1=LICOCENE™ PE MA 4351 maleated polyethylene wax, 5%        maleic anhydride, from Clariant    -   PE/MAH-2=RETAIN™ 3000 copolymer of ethylene/octene copolymer        grafted with maleic anhydride groups, from the Dow Chemical        Company

Crosslinking Agents

-   -   EPDM=NORDEL™ 4820 ethylene-propylene-diene copolymer, from the        Dow Chemical Company    -   PBD=polybutadiene having high content of vinyl groups from Cray        Valley    -   TAIC=triallyl isocyanurate

Surfactants

-   -   SLES=EMPICOL™ ESB 40 surfactant, sodium lauryl ether sulfate,        from Huntsman.    -   ETHOX=TERGITOL™ 15-S-20 surfactant, nonionic secondary alcohol        ethoxylate, from the Dow Chemical Company.

In the samples described below, sample numbers beginning with “C” arecomparative, and sample numbers beginning with “Ex” are workingexamples. Some working examples also serve as preparative examples ofother embodiments.

PREPARATIVE EXAMPLE 1: MAKING AQUEOUS DISPERSION OF INITIAL POLYOLEFINPARTICLES

An aqueous polyolefin dispersion was prepared utilizing a twin screwextruder (25 mm screw diameter, 48 L/D rotating at 450 rpm) using thefollowing procedure. The hydrocarbon polyolefin and the non-hydrocarbonpolyolefin were supplied to the feed throat of the extruder via aSchenck Mechatron loss-in-weight feeder and a Schenck volumetric feeder,respectively. The liquid crosslinking agent was injected into thepolymer melt zone using Isco dual syringe pumps (from Teledyne Isco,Inc. (Lincoln, Nebr., USA)). The polymers were then melt blended, andthen emulsified in the presence of a first aqueous stream andsurfactant. The emulsion phase was then conveyed forward to the dilutionand cooling zone of the extruder where additional dilution water wasadded to form the aqueous dispersions having solid level contents in therange of from less than 70 weight percent. The initial aqueous stream,and the dilution water were all supplied by Isco dual syringe pumps. Thebarrel temperature of the extruder was set to 140-150° C. After thedispersion exited the extruder, it was further cooled and filtered via a200 μm mesh size bag filter. Particle size analysis was done with theBeckman Coulter LS 13320 Laser Light Scattering Particle Sizer (BeckmanCoulter Inc., Fullerton, Calif.) using the standard procedure. Volumeaverage particle size was obtained.

EXAMPLE 2: MAKING A DISPERSION OF CROSSLINKED POLYOLEFIN PARTICLES IN ANAQUEOUS MEDIUM

Crosslinked polyolefin particles were produced in a modified emulsionpolymerization according to the following procedure. The polyolefindispersion from Preparative Example 1 was diluted to 40 wt % solids witha pH of 4-7. Then 5 ppm FeSO₄ dissolved in water (based on polyolefindispersion weight) was added into the dispersion prior to reaction. Thedispersion was then charged into a 250 mL three-neck flask fitted with acondenser and a mechanical stirrer. The flask was placed in an oil bathat 65-100° C. The stirring rod was inserted through the Teflon adaptorand glass sleeve and connected to the center of the flask. The stirrerrate was set at 200 rpm. Nitrogen was slowly purged through the reactor,and cooling water was turned on to flow through the condenser. Redoxinitiator was tert-Butyl hydroperoxide (t-BuOOH) and a reducing agent.The reducing agent was isoascorbic acid (IAA) unless otherwisespecified. The t-BuOOH and the reducing agent were dissolved indeionized water respectively and then fed into the reactor slowly usingseparate syringe pumps. Finally, the hybrid emulsion was collected byfiltration through a 190 micron filter.

The gel fraction of the resulting dispersions were measured using twodifferent methods. As defined above, in all methods, gelfraction=100*WGEL/WTOT. First, the dispersion was dried to remove water,and the weight of dried dispersion was WTOT.

In gel fraction method A, the dried sample of crosslinked polyolefinparticles was extracted with xylene in a Soxhlet extractor for 18 hoursunder reflux. The dry weight of the material after extraction was WGEL.

In gel fraction method B, the dried sample of crosslinked polyolefinparticles was stirred in toluene for 1 hour at 90° C. The mixture ofsolid material and toluene was filtered through a 75 μm filter. Theweight of material retained on the filter, after drying, was WGEL.

The resulting crosslinked polyolefin particles are described in Table 1below. The crosslinking reaction is characterized by reaction time(RXTIME) and reaction temperature (RXTEMP). The amounts of ingredientsused are characterized as “phr,” which is parts by weight based on 100parts by weight of dry initial polyolefin particles.

TABLE 1 Making Crosslinked Polyolefin Particles C1 C2 Ex. 1 Ex. 2 Ex. 3Ex. 4A Ex. 5 Ex 4B Ex 4C E/OCT-1 81 72 72 72 E/OCT-2 67.5 75 75 75 75PE/MAH-1 15 15 15 15 5 5 5 5 PE/MAH-2 15 10 10 10 10 EPDM 8 8 8 13.5 PBD2 TAIC 2 2 2 SLES 4 4 4 4 4 4 4 4 4 Peroxide (phr) 0.8 0 0.4 0.8 0.80.3^((a)) 0.3 0.3^((b)) 0.3^((c)) RXTIME (h) 4 0 2 4 3 1 1 1 1 RXTEMP (°C.) 95 — 95 95 95 65 65 65 65(a) t-BuOOH/sodium formaldehyde sulfoxylate (SFS) redox pair(b) hydrogen peroxide/isoascorbic acid (IAA) redox pair(c) tert-butyl peroctoate/SFS redox pairC1 is comparative because no crosslinking agent was used. C2 iscomparative because the initial polyolefin particles were not subjectedto the crosslinking reaction with peroxide.

The crosslinked polyolefin particles were characterized, as shown inTable 2 below, using methods described above. The gel fraction (“gelfrac”) was characterized by method A or method B or both. The diameter(“diam”) was measured as described above. The notation “nm” means “notmeasured.”

TABLE 2 Characterizing Crosslinked Polyolefin Particles C1 C2 Ex. 1 Ex.2 Ex. 3 Ex. 4A Ex. 5 Ex 4B Ex 4C gel frac 0 0 31 34 51 nm nm nm nm A (%)gel frac nm nm nm nm 36 87 600⁽¹⁾ 12 36 B (%) diam (nm) 335 335 335 335408 335 335  335 335(1) approximately

The comparative samples had no gel fraction, while the working exampleshad significant level of crosslinked material.

Additional initial polyolefin particles were made and then crosslinkedby the methods described above. Compositions were as shown in Table 3.Crystallinity was measured by DSC, at a scan rate of 10° C./minute,using the area under the crystallization exotherm. The terms “low” and“medium” are comparative terms to compare samples within Table 3, asfollows: “low” means crystallization exotherm less than or equal to 30J/gram; and “medium” means crystallization exotherm above 30 J/gram butless than or equal to 45 J/gram.

TABLE 3 Making Additional Initial Polyolefin Particles Ex. 6 Ex. 7 Ex. 8Ex.9 E/OCT-2 67.5 67.5 79 E/OCT-3 79 PE/MAH-1 15 5 5 5 PE/MAH-2 10 10 10EPDM 13.5 13.5 TAIC 2 2 SLES 4 4 4 2 ETHOX 2 crystallinity medium lowlow low diam (nm) 299 340 326 434

The initial polyolefin particles described in Table 3 were crosslinkedusing the methods described above. The resulting compositions were asshown in Table 4. The suffix “X” denotes the result of the crosslinkingreaction. The label “gel frac” refers to the gel fraction in thecrosslinked polyolefin particle, measured by method “B” defined above.All of the samples labeled “Ex” had sufficient crosslinking to qualifyas working examples of the present invention. “diam” is thevolume-average diameter of the crosslinked polyolefin particle prior toemulsion polymerization.

TABLE 4 Characteristics of Crosslinked Polyolefin Particles Ex 6X Ex 7XEx 8X Ex 9X initial PO particle Ex 6 Ex 7 Ex 8 Ex 9 gel fraction 20⁽¹⁾35 68⁽²⁾ 45 ⁽¹⁾Approximately ⁽²⁾Two samples were measured: both hadeither 68% or higher.

EXAMPLE 3: EMULSION POLYMERIZATION

Composite particles were prepared by a seeded emulsion polymerizationprocess. Each of the above crosslinked polyolefin particle dispersionsof Table 4 was placed into a reactor to be used as a seed forpolymerization of acrylic monomers. The monomers were premixed to form amonomer emulsion and then injected into the reactor over 60 min at 65°C. At the same time, a redox catalyst pair was fed separately into thereactor as a free radical initiator over 90 min. The reaction wasmaintained at 60° C. for 90 min and then allowed to cool to 25° C. andfiltered through a 190 μm filter. In all cases the acrylic monomers werea mixture of methyl methacrylate (MMA) and butyl acrylate (BA), in aweight ratio of MMA:BA of 98.0:2.0.

The characterization of the composite particles after emulsionpolymerization is shown below in Table 5.

Grafting was assessed as follows. Samples (approximately 0.2 gram) weredissolved in 5 g of tetrahydrofuran (THF) for approximately 16 hours atroom temperature (approximately 23° C.). Then 5 g of acetonitrile (ACN)was added to the solution, which then stood for approximately 16 hoursat room temperature. The solution was centrifuged at 70,000 revolutionsper minute for 15 min. The supernatant was filtered and tested in a sizeexclusion chromatograph (SEC) apparatus, using styrene-divinylbenzenecopolymer beads, flowing THF at 1 mL/min, with column temperature of 40°C., and differential refractive index detection. The extracted polymerwas assumed to be ungrafted acrylic copolymer p(MMA/BA). The SEC curvesof detector response versus time for each sample were compared to SECcurves for p(MMA/BA) standard samples of known concentrations. The graphof peak area vs. concentration for the p(MMA/BA) standard samples wasfit to a standard line by the linear least-squares method. Using thatstandard line, the SEC peak area for each sample was converted to aconcentration, which was used to calculate the amount of extractablepolymer from each sample.

In Table 5, the label “PO disp” refers to the polyolefin dispersion,defined in Table 4, that was used as seed for the emulsionpolymerization. The suffix “-S” refers to the result of emulsionpolymerization in the presence of a polyolefin dispersion. “Core: Shell”is the weight ratio of dry crosslinked polyolefin particles to totalweight of (meth)acrylic monomers used. In some samples, Na₃PO₄ was addedto the polyolefin dispersion prior to emulsion polymerization, and theamount shown is weight % based on the weight of the solid polyolefinparticles.

TABLE 5 Characterization of Composite Particles Ex. 6S Ex. 7S Ex. 8ASEx. 8BS Ex. 9S C 7S PO-disp 6X 7X 8X 8X 9X C 7 grafting medium mediumhigh high high medium Core:Shell 85:15 83:17 80:20 83:17 83:17 83:17diam (nm) 299 340 326 326 434 340 Na₃PO₄ (%) 0 0 0.5 0.5 0.5 0.5In Comparative C 7S, emulsion polymerization was performed on thenon-crosslinked dispersion of initial polyolefin particles C 7.

EXAMPLE 4: COMPOUNDING OF COMPOSITE PARTICLES WITH MATRIX POLYMER

The aqueous dispersions of composite particles were spray driedaccording to the following procedure. A two-fluid nozzle atomizer wasequipped on a Mobile Minor spray dryer (GEA Process Engineering Inc.(Copenhagen, Denmark)). The nitrogen pressure to nozzle was fixed at 1bar with 50% flow which is equivalent to 6.0 kg/hour of air flow. Aglass jar was placed under the cyclone with the valve on the bottom ofthe cyclone open. Olefin-acrylic dispersion (approximately 40 wt %solid) was pumped into the heated chamber by an emulsion feed pump. Thespray drying experiment was conducted in N₂ environment with an inlettemperature fixed at 120° C., and the outlet temperature was controlledat 40° C. by tuning the feed rate of the dispersion. The volume meanparticle diameter of the dry powder was measured to be in the range of20-40 μm.

The polycarbonate (PC) used was MAKROLON™ 2405 resin from Covestro.Before compounding, the resin was thoroughly dried for 2-4 hours at 110°C. in an oven. The polycarbonate (PC) resin and the composite particleswere compounded with a JSW TEX28V co-rotating twin screw extruder(L/D=42). The resin and the composite particles were supplied to thefeed throat of the extruder via the gravimetric K-Tron feeders and thenmelt blended. The extruded strand was then cooled and pelletized with agranulometer. The temperature profile of the extruder was set as25-260-270-280-285-280-280-280-280-280-280-280-280° C. (from the hopperto the die) and the compounding was done with a screw speed of 150 rpmand an output of 10 kg/hr.

The compounded pellets were dried 4 hours at 110° C. in a low pressuredryer and injection molded utilizing the Battenfield HM80/120 machinewith the following temperature profile: 280-280-285-290° C. (from thehopper to the die). The holding pressure was set as 200 bars and themold temperature was 80° C. The molds were ejected after a cooling timeof 40 secs.

The modifier materials compounded with the PC resin were the compositeparticles described above and, for comparison, PARALOID™ EXL-2629Jmethacrylate butadiene styrene impact modifier from the Dow ChemicalCompany, (herein “MBS”).

EXAMPLE 5: EXPERIMENTAL RESULTS WITH MODIFIER IN POLYCARBONATE

Samples were compounded and molded as described in Example 4 above, with95% by weight PC and 5% by weight various modifiers. The results of theMFR and the Izod impact tests at various temperatures were as shown inTable 6. “nt” means not tested. The conditions for MFR were 300° C. with1.2 kg load. The amounts of modifier shown are percent by weight basedon the total weight of the compounded PC. “Gate Defect” refers to thepresence of surface delamination in the injection molded bar. Asterisk(*) denotes comparative example.

TABLE 6 Results with 2.5% modifier in PC. Izod results in units of J/cm(ft*lb/in). Modifier: none* MBS* Ex. 7S Ex. 8BS MFR (g/10 20 20.3 19.622.8 mm) Izod at 23° C.  7.0 (13.2)  6.7 (12.5)  6.8 (12.8)  6.7 (12.6)Izod at 0° C.  6.5 (12.2)  6.0 (11.2)  6.7 (12.5)  6.5 (12.2) Izod at−20° C. 3.5 (6.5)  5.6 (10.4) 5.0 (9.3)  6.1 (11.5) Izod at −30° C. 1.5(2.8) 3.3 (6.2) 2.4 (4.5) 5.2 (9.7) Gate Defect no no low no

As shown in Table 6, the compounds with modifier show acceptable MFRresults. The compounds with modifier show equivalent Izod impact withthe non-modified PC at 23° C. and 0° C., and the compounds with modifiershow improved Izod impact at −20° C. and −30° C. The modifiers of thepresent invention (Ex. 7S and Ex. 8BS) show improvement to Izod impactthat is equivalent to the improvement given by the commercial MBS impactmodifier. It is known that MBS modifiers tend to degrade relativelyquickly upon exposure outdoors because of the prevalence of unsaturatedpolybutadiene and aromatic rings in the MBS composition. In contrast,the modifiers of the present invention are expected to resistdegradation due to outdoor exposure because of their polyolefincomposition, which has few or no aromatic rings or unsaturations.

TABLE 7 Results with 5% modifier in PC. Izod results in units of J/cm(ft*lb/in) Modifier: MBS* Ex 6S C 7S* Ex 7S Ex 8AS Ex 9S MFR (g/10 min)17.9 19.4 25.5 20.7 20.8 20.3 Izod at 23° C. 6.1 (11.5) 6.1 (11.4) nt6.7 (12.5) 6.5 (12.2) 6.4 (12.0) Izod at 0° C. 5.5 (10.3) 5.8 (10.9) 6.0(11.2) 6.4 (11.9) 6.3 (11.8) 5.9 (11.1) Izod at −20° C. 5.7 (10.7) 5.7(10.7) 5.7 (10.7) 5.8 (11.0) 5.5 (10.2) 5.8 (10.8) Izod at −30° C. 5.2(9.8)  3.1 (5.8)  3.1 (5.9)  3.0 (5.6)  5.7 (10.6) 4.8 (9.0)  GateDefect no high high low no no

The modifiers of the present invention all gave acceptable MFR and Izodimpact results. Example 6S had the lowest level of crosslinking in thecrosslinked polyolefin particles prior to emulsion polymerization, andthat Example had the least desirable outcome for Gate Defect, among themodifiers of the present invention.

1. A dispersion of composite particles in an aqueous medium, wherein thecomposite particles comprise (I) a crosslinked polyolefin core, and (II)a full or partial shell comprising polymerized units of one of morevinyl monomers.
 2. The dispersion of claim 1, wherein the vinyl monomercomprises one or more (meth)acrylic monomer.
 3. The dispersion of claim1, wherein the vinyl monomer comprises one or more unsubstituted alkylester of (meth)acrylic acid.
 4. The dispersion of claim 1, wherein thecrosslinked polyolefin core comprises one or more hydrocarbon polyolefinand one or more non-hydrocarbon polyolefin.
 5. The dispersion of claim1, wherein the crosslinked polyolefin core has Tg of −30° C. or lower.6. The dispersion of claim 1, wherein the crosslinked polyolefin corehas gel fraction of 10% or more by weight.
 7. The dispersion of claim 1,wherein the crosslinked polyolefin core is present in an amount of 60%to 90% by weight based on the sum of the weight of the crosslinkedpolyolefin core and the weight of the shell.
 8. The dispersion of claim1, wherein the amount of the shell that is grafted to the core, byweight based on the total amount of the shell, is 40% or more.